Gauges are used in vehicles and in other assemblies to selectively provide and to display certain information to the operator and/or user of the vehicle or assembly. For example and without limitation, gauges are used to provide the driver and/or passenger of a vehicle with information such as the speed of the vehicle (e.g., a speedometer); the speed of the vehicle's engine (e.g., a tachometer); the amount of gas or other fuel remaining in the vehicle (e.g., a "fuel gauge"); the oil pressure within the vehicle's engine (e.g., an "oil gauge"); the voltage output of the vehicle's battery (e.g., a "battery gauge"); and the temperature of the vehicle's engine (e.g., a "temperature gauge"). Typically, this information is provided by the use of respective and selectively movable pointers. It is desirable to have the information provided by these gauges to be relatively accurate.
Typically, many of these gauges include a microprocessor and/or micro-controller which receives data (e.g., resistance or signal frequency data), from one or more vehicle sensors or modules, representing some or all of the foregoing information (e.g., vehicle and engine speed, fuel contained within the vehicle, or existing oil pressure). The micro-controller utilizes this received information to calculate a desired and correct position for the respective gauge "needle" or pointer and selectively transmits data representing this position to the gauge driver which selectively moves the respective gauge pointer to the desired and correct position. Typically, the micro-controller transmits a plurality of discrete signal pulses or "counts" which cause the gauge driver to move the pointer to a position or angle which is based on and/or is uniquely associated with the number of "counts" which are received.
Each of these prior gauges generally and further includes a "pointer stop" or "post", upon which the gauge pointer rests when the gauge is not "energized" (e.g., is not receiving signals from the micro-controller). A "hold at zero" apparatus typically includes a mechanical or magnetic device and is typically used to hold the pointer against the pointer stop when the gauge is not energized. One mechanical "hold at zero" apparatus, which is used by some other types of gauges, is a "tip heavy pointer". Particularly, in this arrangement, a weight is placed upon the "tip" of the end of the pointer, effective to hold the pointer against the pointer stop by the use of gravitational forces acting upon the weighted tip. One type of magnetic device which is used by still other types of gauges is a "hold at zero" (or "HAZ") magnet, which is a small magnet which is effective to hold the pointer against the pointer stop through magnetic force or attraction.
These prior gauges suffer from several drawbacks which reduce their respective accuracy. For example and without limitation, these gauges typically suffer from a pointer placement offset error. Particularly, pointer placement offset errors arise when the unenergized or "electrical zero" position of the pointer of the gauge is not selectively positioned or "set" to the position on the gauge display corresponding to and/or representing the "zero value" of the display or the "mechanical zero" position (e.g., typically the "mechanical zero" position on a tachometer gauge corresponds to 0 revolutions per minute while the "mechanical zero position" on a speedometer gauge corresponds to 0 miles per hour). The pointer placement offset error is then equal to the number of "counts" or signals that must be received by the gauge driver to move the pointer from the "electrical zero" position to the "mechanical zero" position (or the corresponding number of degrees which the pointer must move in order to be selectively positioned upon the "mechanical zero" or "zero value" display position).
Furthermore, these prior gauges typically suffer from errors caused by their respectively employed "hold at zero" apparatus. These "hold at zero" errors are typically equal to the number of driver "counts" or signals required to offset or "cancel out" the gravitational effects of the tip heavy pointer or the magnetic effects of the HAZ magnet upon the rotor magnet of the gauge driver. These "hold at zero" errors typically vary depending upon the angular position of the pointer (for gauges using a tip heavy pointer) or for the position of the HAZ magnet in relation to the rotor magnet (for gauges using a HAZ magnet).
If not corrected or compensated, these errors will cooperatively and cumulatively cause the gauge to display significantly inaccurate information which could cause a variety of problems or difficulties for the vehicle's driver and other occupants. For example and without limitation, an inaccurate fuel gauge could cause a driver to undesirably "run out of gas"; an inaccurate tachometer could cause a driver to shift the vehicle at improper moments resulting in unnecessary wear to the vehicle's engine; an inaccurate temperature gauge could cause a driver to unknowingly "overheat" the vehicle's engine; and an inaccurate speedometer could cause a driver to unknowingly violate a "speed limit".
There is therefore a need for a new and improved gauge assembly which provides a relatively accurate and selective display of desired information, which corrects pointer placement offset errors and "hold-at-zero" errors, and which provides these benefits in a relatively cost effective manner.